Forming pattern or form bar



Oct. 18, 1960 R. c. HATHORN EI'AL 2,956,318

FORMING PATTERN OR FORM BAR Filed May 27, 1958 POYCHATHORN GORDONL.TURNER INVENTORS United States Patent FORMING PATTERN OR FORM BAR RoyC. Hathorn, 1309 Kilby Terrace, and Gordon L. Turner, P.0. Box 133, bothof Anniston, Ala.

Filed May 27, 1958, Ser. No. 738,061

9 Claims. (Cl. 22-22) This invention relates to mold forming apparatusand particularly to a pattern or form bar for forming hollow molds andcompacting and shaping mold forming material within hollow flasksemployed in casting hollow cylindrical products, such as cast iron soilpipe, or the like.

More specifically the present invention relates to a sand or other moldforming material compacting pattern or mandrel particularly adaptablefor use in machines for centrifugally casting hollow cylindricalproducts and may be employed in various types of such machines now onthe market, one such machine or apparatus being disclosed in Patent No.2,449,900 issued September 28, 1948,

to L. L. Johnston.

In the forming of molds for use in casting cylindrical objectsdilficulty has been heretofore encountered in maintaining concentricitybetween the flask and the mold cavity and in providing uniform hardnessthroughout the entire mold, so as to produce a cast product of uniformthickness and true concentricity throughout, and various forms of moldforming bars or patterns have been devised to provide such results, onesuch being disclosed in Patent No. 2,449,387 issued March 7, 1950. Whilethe mold forming bars or patterns heretofore devised have in somemeasure improved on the formation of the sand molds, they have notsatisfactorily overcome the difliculties.

While the mold forming bars or patterns of the type just referred, toprovide very concentric molds, their use occasions much trouble with thediameter of the mold due to the fact that the mandrel or pattern isloaded on one side. Any variation in moisture or green compressionstrength of the sand used for making the mold is reflected in variationof load on the mandrel or pattern causing the mandrel to deflect morewith dry sand and less with wet sand. This brings about a variation ofmold diameter which limits the minimum mold diameter that can be made.

The mandrels or forming bars now in use whip or are subject todeflection when in use resulting in lack of uniform concentricitybetween flask and mold cavity and thick and thin walls of the moldcausing uneven thicknesses and lack of uniform outer surface of the castproduct. Various shapes of mold forming bars have been provided tocompensate for such whipping or deflection of parts of the mandrel orforming bar, but since such deflection of the forming bar is not aconstant at all operating conditions such devices cure the fault onlypartially and often not at all.

The present invention provides a pattern or forming bar which under alloperating conditions will provide a mold of uniform thickness andhardness throughout and one which is so shaped that symmetrical loadingon the bar is provided which results in uniform concentricity betweenthe flask and the mold cavity, thereby producing a product of uniformthickness, and straight outer surface throughout, as well as one whichirrespective of variation of moisture or green compression strength ofthe sand used, will provide correct, desired and uniform diameters ofmold, even in small diameter pipe.

With these and other objects in view, as may appear from theaccompanying specification, the invention consists of various featuresof construction and combination of parts, which will be first describedin connection with the accompanying drawings, showing a forming patternor form bar of a preferred form embodying the invention and the featuresforming the invention will be specifically pointed out in the claims.

In the drawings,

Figure 1 is a longitudinal section through a flask showing the patternor forming bar therein, in side elevation.

Figure 2 is a cross section through the flask, mold and forming bartaken on the line 22 of Figure 1.

Figure 3 of the drawing is a cross-section,'similar to Figure 2 onlyshowing a modified form of the forming bar or mandrel.

Figure 4 is a view similar to Figures 2 and 3 only showing a stillfurther modified form of the forming bar or mandrel.

Referring more particularly to the drawings, there is shown acylindrical flask 1 formed of any suitable material (preferably castiron) and as is used in centrifugal casting machines as above referredto. The flask 1 has the usual one or two enlarged end portions 2 topermit formation of the hell or bell ends of a pipe cast therein.-

While in the drawings the flask 1 is shown as having both its endsenlarged, it is to be understood that'the present invention is notlimited for use in such specific flasks, but

embodies the use of various forms of flasks, such as those of uniformdiameter throughout, or with only one enlarged end.

Cooperating with the flask to form a mold therein such;

shown in Figure 2 of the drawings and it has a maximum diametersubstantially equal to the interior diameter of the mold to be formed inthe flask 1, with a minimum diameter a predetermined amount less thanthe maximum diameter.

The minimum diameter of the forming bar 4 is such that substantiallycrescent shaped spaces, indicated at 6 are provided within the interiorof the mold at opposite sides of the forming bar 4. The forming bar 4and any enlargements on its ends are elliptical throughout their entirelength, and the forming bar 4 proper is of uniform diameters of varyingradial degrees throughout its entire ength.

The flask and forming bar 4 are adapted for use with various type ofcentrifugal casting apparatus or machines on the market and in someinstances the flask 1 will be rotated during formation of the mold andin others the forming bar 4 will be rotated, depending upon conditionsand the particular type of apparatus with which the flask 1 and formingbar.4 are used. The effectiveness and efficiency of the forming bar isequal in either instance.

In operation the flask is positioned to receive sand;

or other mold forming material and the forming bar 4 is inserted axiallyinto the mold and held therein by outside means (not shown). Suchholding means depends upon the type of casting apparatus with which theforming bar is used. After the forming bar 4 is axially located in theflask, either the flask 1, of the forming bar 4 is rotated, againdepending upon the type of casting apparatus with it is used. Duringsuch rotation sand is blowin into the flask from one end. The rotarymotion causes successive formation of the crescent shaped spaces 6 aboutthe in- Patented Oct. 18, 1960 the'bar; 4 rotates within the flask 1,the crescent: shaped spaces (St atany givenpoint' relative to the flask1 open and close, and itsclosing action forces the sand outward.

or radially resulting in compacting the sand and toelimh natevoid's orsoft spots in the-sand mold, as well aspro-.

vidinga mold of uniform thicknessthroughout its length. The rate ofpulsation or opening and closing of the spaces 6 is controlled by thespeed of rotation of eitherthe flask 1- orforming bar 4 and thereforethe moldhardness may be very closely controlled. rectly proportional toreduction in cross sectional area of the mold creates a strong tendencyto center the forming bar 4' in theflask 1. In other words, if theforming bar or pattern 4i's oft center or eccentric with the'flask 1 andthe sand mold becomes harder on the thin side (formed because of'theeccentric position of the forming bar 4') the forming bar 4 will beforced back to center of the flask 1. d

This concentn'city of the mold will be maintained within very closelimits which is necessary for good results in centrifugal casting.

Whe-n large patterns or forming bars 4 are used for making largediameter cylindrical products the above procedure is varied slightly.

In such instances the flask 1 and forming bar 4 are stationary whilesand in a measured quantity is injected into the flask. After the sandis injected into the flask the rotation is started and due to theelliptical cross secion formation of the forming bar 4 the sand will becompacted to the desired mold hardness, with uniformity oft-he moldthroughout and freedom from soft spots or .voidswith a few rotations, insome instances one or two complete turns of the forming bar 4 or flask1.

Thus it will be seen that by providing a forming bar of elliptical crosssection with its maximum diameter substantially equal to the desiredinterior diameter of the rnold to be formed and its minimum diametersuch as to provide the substantially crescent shaped sand receivingspaces great flexibility of use is provided, permitting its use to coverthe entire range of soil pipe from 2" diameter through 15" diameter, thesize of the forming bar! and its various diameters being dependent ofcourse npon'the size of pipe to be cast.

While in the foregoing the mold forming bar or mandrel has beendescribed as elliptical in cross section and forming crescent shapedsand receiving recesses or pockets in advance of the sweeping maximumdiametrical portions of the bar, it is'to be understood that moldforming bars of cross section other than elliptical (but not round) maybe employed so long as such cross-sectional configuration is symmetricalabout its axis and provides sand receiving recesses, confined betweentwo major diameter portions of the bar and in advance of a successivesweeping major diametrical portion.

In Figure 3 of the drawings the mold forming bar 20 is shown astriangular in cross section with its apices rounded as shown at 21. Withthe mold forming bar or mandrel triangular in cross section three sandreceiving recesses, 22 are formed in the mold 23, each spaceconfinedbetween two major diameter portions of the bar, as are thecrescent shaped recesses or spaces 6 confined between two major diameterportions of the el1ipti- Mold hardness being di-.

cal bar 4, so that upon rotation of either the mold forming bar 20 ortheflask 25 the action will be the-same as that hereinabove described inconnection with the structure shown in Figures 1 and 2 of the drawings.

Figure 4 of the drawings shows a mold forming bar or mandrel 30 which issquare in cross section with its mold surface engaging corners rounded,This form while providing four points of major diameter and four sandreceiving spaces or pockets operates. in the same: manner as the formsof the invention shown in Figures 1, 2 and 3 of the drawings;

The present invention is not limited in use to-the making of moldsfor'centrifug-al casting, but may be employed in making cores forfoundry use or for compacting any practical material in cavities.

What is claimed is:

1. Mold forming apparatus comprising a flask adapted 7 to contain ahollow body of mold form-ing material, and

a mold forming bar extending axially within said flask,

said mold forming bar beingnon-circular incross section and shaped to besymmetrical of its axis to form a-true geometrical figure in crosssection and free'of surfaces projecting beyond its true geometricalsides and topro vide in each cross-sectional plane thereof at least twoportions of major radius andat least two portions ofminor radius to formsand receiving recesses between said major and minor radius portions inthe flask each of said major radius portions connected to aminor radius:portion by a convexly curved surface, whereby in use sand will be sweptfrom the spaces into uniform compact thickness within the flask.

2. Mold forming apparatus as claimed in claim 1,

wherein saidmold forming bar has at least one enlarge ment on its endsof the same cross-sectional configura tion as the bar.

3; Mold? forming apparatus as claimed in claim 1,

wherein said mold forming bar is elliptical in cross sec. tion and ofuniform maximum and minimum diameters.

throughout its length.

4. A mold forming bar as claimed in claim 1, where-.

wherein said mold forming bar is elliptical in cross sec tion.

7. Mold forming apparatus as claimed in claim 1, wherein said moldforming bar is substantially square in cross section.

8. Mold forming apparatus as claimed in claim 1, wherein said moldforming bar is substantially triangular.- in cross section.

9. A mold forming bar as claimed in claim 3, having at least oneenlargement on its ends, said enlargement" being elliptical in crosssection.

References Cited in the file of this patent UNITED STATES PATENTS402,029 McNeal et' a1. Apr. 23, 1889 1,302,816 Lemoine May 6, 1919'2,499,387 Johnston Mar. 7, 1950 FOREIGN PATENTS 193,075 Germany Dec. 13,190-7.

